Suitable for hydraulic retarders matched with ZF 12-speed gearboxes, elaborately made of high-hardness wear-resistant alloy with solid texture and good wear resistance, enabling smooth reciprocating movement without jamming. Strict size control and tight fit with sealing accessories ensure fast and even oil pressure transmission and sensitive braking response. It can withstand long-term high-pressure operation with excellent high temperature resistance and aging resistance, performing stably in frequent braking scenarios on long downhill mountain roads. It outputs balanced braking torque steadily to meet daily braking demands of heavy-duty vehicles.